The Macbook's screen may have the perfect screen size, but the weight and battery life suck. It's 5.2lbs - that's very heavy for a laptop of this size. It's also unlikely that you will get more than 2.5hrs out of the battery, especially if you use it at full brightness.
Many other laptops are available today that are much lighter, with longer battery life - the Thinkpad X60s, for example. It weighs 2.7lbs and can get ~7 hours battery life.